If this was your first flip, I applaud the boldness of tackling a 4 unit! 

So either be prepared to lose more than half of the numbers you wanted skip traced or be prepared to tackle this obstacle with a different marketing strategy.Also also, (yes meant that twice), a good amount of the people that call you back are calling because they had a missed call- not because they've listened to your msg.Again, platforms etc....I won't get into all of these individually as this post is way longer than expected, but feel free to msg me directly with any questions or clarifications. 

I am unsure how to tackle this issue and hoping I can get some advice so I do not end up costing myself more time and money.I have a tenant that has never paid rent on time and is currently behind on payments.

The model for the last year has been putting the biggest fires out first and letting the smaller ones lie until I have the time to tackle them.

I do think it's a good learning experience for an investor to tackle at least once because by the nature of being able to be either redeemed out or taking title for whatever exit purposes you are thinking, it's a relatively safe prospect.  

And lastly, if you go that route, ideally try to make $100-$150 cash flow per bedroom in your home after the mortgage (P+I+taxes) -- but if your rents could cover your mortgage, and give you just a small margin of profit. then I would choose the heloc, you go rent somewhere else, and then wait to utilize the capital based on the project you feel comfortable with and want to tackle.  

Which niche I should tackle.

Also a lot of them do not have the work ethic/mindset to tackle this aspect of RE and be successful.

I believe trying to tackle all of this might be too overwhelming in a short period of time.

Are you a systems guy ready to tackle property management?